German carmaker Opel, a subsidiary of General Motors, found itself in the spotlight on May 13, with the transport ministry demanding explanations for media reports alleging irregularities in the emissions values of some of its cars.
According to both the weekly magazine Der Spiegel and the investigative news program Monitor on ARD public television, tests on a number of Opel's diesel models had uncovered "hitherto unknown devices" that deactivate filtration systems in the engines of two of the best-selling models, Astra and Zafira.
That meant that the models' emissions systematically exceeded norms.
In response to the revelations, a special committee set up in the wake of the massive engine-rigging scandal that has engulfed Volkswagen, "has invited" Opel to offer an explanation, a spokesman for the transport ministry said.
Opel issued a statement denying it used the same emissions-cheating software that is at the center of the VW scandal.
"Our software was never programmed to deceive or defraud," insisted the carmaker, which is just emerging out of long years of crisis.
"Emission control systems are highly complex integrated systems," Opel said.
"The various parameters such as engine speed, load, temperature and altitude play an essential role and are interrelated. Such a complex system cannot be broken down into individual parameters. Interactions must be understood holistically, in combination with the prevailing conditions and the various areas of the control system," it said.
The government committee, which has in recent months analyzed all diesel models similar to those involved in the VW scandal, has concluded that no similar fraud has taken place.
Nevertheless, in a certain number of vehicles, the emission control systems were systematically de-activated when the outside temperature dropped below a certain level.
This is only allowed under European rules to prevent possible accidents or damage to the engine.
In April, German makers, Audi, Mercedes, Opel, Porsche and Volkswagen, decided to voluntarily recall around 630,000 cars in Europe to remedy this problem.
According to Der Spiegel and Monitor, the Astra's emission control systems were only programmed to function at outside temperatures above 17 degrees Celsius, effectively meaning they did not function for a large part of the year.
VW was plunged into its deepest-ever crisis last September when it emerged that it had installed emissions-cheating software, known as defeat devices, into 11 million diesel engines worldwide.
Copyright Agence France-Presse, 2016